The present invention concerns a hydraulic dashpot.
Hydraulic dashpots are employed to attenuate the motions of wheel suspensions articulated by way of springs, preferably in motor vehicles.
The dashpot comprises a cylinder is charged with shock-absorbing fluid and a piston that travels back and forth inside it and divides it into two chambers. The attenuation is created by forcing fluid out of one chamber and into the other through preferably resiliently loaded ports in the piston.
In one known dashpot, bypasses that hydraulically parallel the ports and provide communication between the chambers allow the motion to be attenuated at narrow and precise increments. Bypass cross-sections of different widths are also known for this purpose.
European Patent 1 006 292 A1 discloses a dashpot of this genus. The bypass between the two chambers is accommodated in an axial bore in the piston rod and provided with radial outlets through it. The cross-section of the bypass can be varied by means of a rod that engages a needle valve. The drawback to this embodiment is that only a constant cross-section can be established, and the fluid will flow through the same cross-section no matter whether the piston is traveling in the compression or in the suction direction.
Blocking the fluid as it flows in one direction or the other is also known. The drawback to this approach is that the flow can be controlled in only one direction.
German 10 138 487 discloses a generic hydraulic dashpot wherein the bypass can have one width while the piston rod is traveling in the compression direction and another independent width while it is traveling in the suction direction. Unfortunately, the controls employed for this purpose are extremely complicated. Furthermore, the cross-section of the bypass is established indirectly and is accordingly with considerable difficulty.
The object of the present invention is a dashpot of the aforesaid genus wherein the bypass cross-section can be easily established manually, whereby both the means of establishment and the overall dashpot are uncomplicated.
The particular advantages of the present invention are, first, that the bypass cross-section associated with the compression phase flow and the bypass cross-section associated with the suction-phase flow can be established entirely independently and, second, that the dashpot is simple in design.